That's what I've been saying, except, I disagree that the oil temp is the better indicator of that. The parts have reached the engine operating temp by the time the thermostat opens, that's the reason why it stays closed until that time, so that engine temp can be reached faster.
By the time the oil absorbs enough heat to get it to this magical 240F, the engine is well into being warmed.
The engine/coolant temp is the better indicator, but we don't have one, and that sucks.

The issue with using water temperature as a guide is that it only indicates how hot the top of the engine is, virtually all the heat is created around the combustion chamber. If you have ever had a water pump fail, you will know that the coolant in the cylinder head can boil in a matter of seconds, without circulation.

With cars I've had in the past with full instrumentation, the water temperature will reach normal temperature about twice as fast as the oil. At this point the top end of the engine will be pretty close to thermal equilibrium, but until the oil is up to normal operating temperature, it will be cooling the big-end bearings and preventing them from reaching equilibrium.

If the big-end of aluminium connecting rods are not at the normal operating temperature of about 100C, but at about 60C (likely the approximate bearing temperature when the coolant has just reached 100C, as no coolant reaches the bearings, they are oil cooled), then they will be running tighter than at thermal equilibrium.

Aluminium has a thermal expansion coefficient of about 22x10^-6/C, steel has a coefficient of thermal expansion of about 12x10^-6/C. This means that a 50mm diameter journal bearing will be 0.02mm tighter at 60C than at 100C. Engines with big end bearings of 50mm diameter require a bearing clearance of about 0.06mm when the engine is built at room temperature (nominally 20C), so at 60C the clearance will be 0.08mm and at 100C 0.10mm. With the oil not circulating as well at 60C compared with 100C (of course this can be seen by the oil pressure, which is directly linked to oil temperature at a given pump speed, ie engine speed for mechanical pumps), the flow rate will be lower and the pressure higher due to both oil viscocity and the tighter space to squeeze through in the bearings.

I will not run the engines of my cars at high RPMs until thermal equilibrium has been reached and the oil is lubricating the big ends at the optimum bearing clearance.

Those of you that have your 1's for a while in cold weather, how long does it take for you to get warm then hot air from the HVAC in winter temps?
By winter, I mean at least 32F and below.

As I use an E46 with proper tires for cold weather, I can only report down to about 40oF. At that ambient temp, my 128i begins to provide warm air and the AUTO fan speed starts increasing after about 7/10 mile of driving at 20~25 mph speeds on neighborhood streets. (I normally begin driving within 20 seconds of starting the engine.)

The issue with using water temperature as a guide is that it only indicates how hot the top of the engine is, virtually all the heat is created around the combustion chamber. If you have ever had a water pump fail, you will know that the coolant in the cylinder head can boil in a matter of seconds, without circulation.

With cars I've had in the past with full instrumentation, the water temperature will reach normal temperature about twice as fast as the oil. At this point the top end of the engine will be pretty close to thermal equilibrium, but until the oil is up to normal operating temperature, it will be cooling the big-end bearings and preventing them from reaching equilibrium.

If the big-end of aluminium connecting rods are not at the normal operating temperature of about 100C, but at about 60C (likely the approximate bearing temperature when the coolant has just reached 100C, as no coolant reaches the bearings, they are oil cooled), then they will be running tighter than at thermal equilibrium.

Aluminium has a thermal expansion coefficient of about 22x10^-6/C, steel has a coefficient of thermal expansion of about 12x10^-6/C. This means that a 50mm diameter journal bearing will be 0.02mm tighter at 60C than at 100C. Engines with big end bearings of 50mm diameter require a bearing clearance of about 0.06mm when the engine is built at room temperature (nominally 20C), so at 60C the clearance will be 0.08mm and at 100C 0.10mm. With the oil not circulating as well at 60C compared with 100C (of course this can be seen by the oil pressure, which is directly linked to oil temperature at a given pump speed, ie engine speed for mechanical pumps), the flow rate will be lower and the pressure higher due to both oil viscocity and the tighter space to squeeze through in the bearings.

I will not run the engines of my cars at high RPMs until thermal equilibrium has been reached and the oil is lubricating the big ends at the optimum bearing clearance.

The oil temp gauge has no indication for anything other than temp.
It doesn't show a yello, green, or red zone.
That isn't by mistake. If waiting until the oil temp reaches 240F before normal driving can be done, then why is that not indicated?
Why is it not part of all automobiles operating directions?
And, in this age of superior engine manage, it would be really easy to limit RPM based on oil temp. But, it's not done.
This issue of oil temp is being overstated, and it's because the 1 has an oil temp gauge and no coolant/engine temp gauge.
Also, notice that the oil temp gauge starts at 160F, very close to the typical 170F of most thermostats.

At 77F ambient temp, it takes my 135i about 5-6 minutes of driving at an avg. of 50mpg to get the oil temp gauge to start moving from the 160F position. If we were to wait until we hit 240F-250F, in the winter with 10F, we'd be near to our 15 mile destination before we could actually drive normally. I hope no one has to actually use half throttle to avoid an accident during that drive, as they would think their damaging their engines doing so with this overstated issue.

Your knowledgeable thermal metallurgical post is good, but doesn't prove that the oil temp has to reach 240F before the oil is providing proper lubrication to the needed parts. Modern engines are built with much tighter tolerances than they were back when. Bearing clearance and heat expansion rates are considered when designing an engine. And, if oil temp were that big of a factor, it would be given much more consideration than a simple gauge that indicates nothing other than temperature.

Even way back in the days of using standard oil, daily driven cars went with the coolant/engine temp gauge. Modern oils, and especially synthetics are quite superior lubricants. Synthetic even flows easily at 32F. I've not found data to show that synthetic at even 100F is not providing proper lubrication and protection, nor that it provides better service once it hits 240F.

The other lack of data is that we don't see the large number of engines with bearing failures due to driving normally before the oil has reached 240F.

I didn't read in your post at what temp you feel it's safe to drive normally.
I'm guessing that you support waiting until the oil temp gauge reaches 240-250F.
I'm not saying that one doesn't need to take into account engine warmup before hitting the loud pedal. We're just disagreeing on when that is from a cold start. The ingrained engine wisdom of the 60's and 70's is still alive today. For example, look at how many people still buy into the 3000 mile oil change interval even when using synthetic.
But, many of us have moved on from that, and so have the companies that make these modern automobiles.

The oil temp gauge has no indication for anything other than temp.
It doesn't show a yello, green, or red zone.
That isn't by mistake. If waiting until the oil temp reaches 240F before normal driving can be done, then why is that not indicated?
Why is it not part of all automobiles operating directions?
And, in this age of superior engine manage, it would be really easy to limit RPM based on oil temp. But, it's not done.
This issue of oil temp is being overstated, and it's because the 1 has an oil temp gauge and no coolant/engine temp gauge.
Also, notice that the oil temp gauge starts at 160F, very close to the typical 170F of most thermostats.

In the Z4M the variable redline indicator on the tach doesn't reach the maximum until the oil temperature reaches 75C (167F), it's first major mark is at 50C, so BMW expects the oil to be at least at 75C before using the full rev range. For the Z4M the manual states that normal oil operating temperature is between 80C and 120C, with 100C being the centre position. All current oil specs quote the viscocity at 100C, so for example, a 0w40 oil is thicker than 40 weight below 100C and flows less easily, with a higher likelihood that the oil pump won't be able to pump a high enough volume of cold oil to keep the engine well lubricated at high revs.

I don't use the maximum rev range until the oil is at normal temperature, i.e. 80C, or beyond 120C (which I haven't reached on the track yet, it maxes out at about 115C under very hard use). It is interesting that BMW considers that oil temperature is more important in the ///M cars than water temperature.

With the 135i, I'll use a similar philosophy, when we receive the car in a couple of months.

For any engine, running it hard with cold oil will cause more stress on the components, it just depends on how much risk of wear you are willing to tolerate.

RPM90. Just as stated we are not waiting till peak temp to thrashing our engines but do make sure it hits a general operating temperature. You qoute about modern engineering accounting for all of this but then argue that old day techniques like your coolant gauge are the way to monitor this. Our coolant heats faster than the metals in our engine. I've seen coolant and oil gauges read in numbers or colors or from humbum to yehaa.. Just because it's not painted like you think it should be, doesn't mean it's a useless instrument. The same engineers you trust to account for thermal expansion are the ones that chose an oil gauge and not a temperature gauge for your engine and apparently they are being paid a little more for their opinions than you. Your engine is not near the temperature it's engineered for max life/performace at the point when your thermostat opens up. Coolant heats and cools too quickly to measure the temperature of your engine during it's closed loop/inital cooling stages where all the heat it is absorbing is from the head/combustion chamber, that's why we use it as a COOLANT. It's like saying there was one successful combustion in a cylinder of your engine and it was at the right temp so now your car is operating at temperature. You are allowed what ever opinon you would like. And you paid for the car so drive it however you perfer. but no matter how you drive, your warrenty will be long gone by the time you find which way was right or wrong. At least there will be plenty of people with fine operating cars that can help pull you to the junkyard.

RPM90, I don't know who told you they wait until the oil gauge says 240 before they gun it. But its bull shit. My gauge didn't pass 230 tonight after a 20 min drive in 65 degree weather.

Mine is the same way. I rarely hit above that.

BTW, those of you who don't wait till the oil temp gauge is fully at the high temp point, are not the ones I'm addressing.

There have been posts on this thread as well as others where folks are overly concerned about driving their car, it seems not much past idle rpm, until they reach this magical temp. And, many say it takes them about 15 minutes of more to get there. My 135i even in the 60's ambient doesn't take that long for the oil temp gauge to start moving.

RPM90. Just as stated we are not waiting till peak temp to thrashing our engines but do make sure it hits a general operating temperature. You qoute about modern engineering accounting for all of this but then argue that old day techniques like your coolant gauge are the way to monitor this. Our coolant heats faster than the metals in our engine. I've seen coolant and oil gauges read in numbers or colors or from humbum to yehaa.. Just because it's not painted like you think it should be, doesn't mean it's a useless instrument. The same engineers you trust to account for thermal expansion are the ones that chose an oil gauge and not a temperature gauge for your engine and apparently they are being paid a little more for their opinions than you. Your engine is not near the temperature it's engineered for max life/performace at the point when your thermostat opens up. Coolant heats and cools too quickly to measure the temperature of your engine during it's closed loop/inital cooling stages where all the heat it is absorbing is from the head/combustion chamber, that's why we use it as a COOLANT. It's like saying there was one successful combustion in a cylinder of your engine and it was at the right temp so now your car is operating at temperature. You are allowed what ever opinon you would like. And you paid for the car so drive it however you perfer. but no matter how you drive, your warrenty will be long gone by the time you find which way was right or wrong. At least there will be plenty of people with fine operating cars that can help pull you to the junkyard.

I've been driving for a long number of years and have worked on cars for the same number. I'm not pulling this out of thin air. I use the information that others before me have accumulated over the years, and I benefit from their knowledge by learning what they say and then use my own experience by which to decide what to do. I've NEVER had an engine failure in all these years, and have always used the coolent/engine temp gauge to let me know when it's ok to get on it a bit.

You can wait until your oil gauge reaches what ever temp you are comfortable with. I'm not telling you you're wrong. I'm simply saying that when you take more into account then just oil temp, there are different factors to consider when making YOUR decision. On my end, I don't go with feelings about mechanical issues, I like to go with mechanics and science, and data.
Show me where you can't use engine/coolant temp as a gauge for when you can safely rev your engine? I've not read that as a general consensus. I'd welcome reading that information. I'm open to learning and changing my mind.
Mind you, I don't recommend WFO throttle and redline in every gear for the first 5-10 minutes on a cold engine, so let's not overstate this.

The current inclusion of an oil temp gauge is a newer addition in modern BMW. My 2003 didn't have it. Including certain gauges while leaving others out is not necessarily only an engineers decision. However, farther down I write about what the oil gauge may be taking into consideration, might be.
For an example of how marketing can affect engineering, take gearing for example. An engineer would select gearing to best optimize the way the engine builds it's power band to optimize performance, even if that performance would mean using 3rd gear to get to 60mph. However, many if not most gearing is chosen for that all important 0-60 time, as that helps sell cars.
If the engineers were allowed to put in the gauges they want, I'll bet they would include a coolant temp gauge, oil pressure, oil temp, boost pressure, etc...

I can't say why they choose an oil temp gauge this time while leaving out coolant temp or even oil pressure. Considerations are space available for dash design, cost of including gauges and their sensors and wiring, it could even be to give the car a more "sport" appearance to differentiate it from the norm, etc... I will say that I think it's more cost and marketing driven, and we have some high heat producing turbo's, so it's a "cool" inclusion too. It's not a commonly used gauge in daily driven cars like the coolant/engine temp gauge. It does have a certain cache though in "sport" cars.

I don't know how you draw a conclusion that a coolant temp gauge is "old school". Knowing your engines operating temp is still important. Also, I didn't say that the oil temp gauge is worthless, pointless, or useless. If I did then I misspoke and didn't want to say or imply that. I'm more concerned that the coolant/engine temp gauge was left out. Also, it seems people are now overly concerned about when they can drive their cars, and sense the oil temp gauge is the one that's right there, people don't have another gauge to use. However, it's a safe bet that you don't need the extensive warm up of engines of the past. It's been a BMW recommendation for at least a decade now to start the car and start driving slowly as soon as you start the engine, as that warms up all the whirly bits quicker.

The other important factor that is being somewhat ignored is that we're running full synthetic oil that has vastly better performance with low temp viscosity being a very important factor. Why? Because synthetic can flow and protect are much lower temps than non synth, even before the oil reaches hot temps.

Your engine is not near the temperature it's engineered for max life/performace at the point when your thermostat opens up.

Again, show me where that's true? What document did you read for that?

Coolant heats and cools too quickly to measure the temperature of your engine during it's closed loop/inital cooling stages where all the heat it is absorbing is from the head/combustion chamber, that's why we use it as a COOLANT.

I don't really understand what point you're making here.
Cold start, closed loop operation is not an "initial cooling stage". It's the initial heat up stage. During this mode coolant is not flowing, and the cats are being heated quickly for emissions. The coolant isn't moving so that it doesn't cool. It's designed this way to allow the engine to warm up first.

The cooling system in a car is under pressure so as to raise the coolants boiling point, meaning it takes a greater amount of thermal energy to get the coolant to it's boiling point, thus increasing it's cooling efficiency.
In "closed loop" mode the flow of coolant is stopped. Why? So that the engine can build up heat and warm the whole engine NOT just the top of the engine. By your very comments, think about what you just said and what is happening in this warm up mode.
The coolant is not circulating, thus it is not removing heat from around the whole engine, thus those parts ARE heating up quickly. You don't want to remove heat in cold closed loop running, because you want the heat buildup. Then when the coolant/engine reaches it's operating temp the thermostat opens to begin cooling the engine parts. WHY? Because if the engine temp is allowed to keep increasing you're combustion efficiency goes down, also as temps rise there is greater frictional heat buildup that leads to the oil losing it's viscosity, which is detrimental to moving parts.
Luckily, synthetic helps here as well as it holds its viscosity beyond conventional oil, which will begin to breakdown, and if it's allowed to get even hotter it will reach it's flashpoint where the oil will burn and can lead to formation of solids on bearings and parts in close contact. Heat is the enemy to proper engine function, not the other way around.

Engine temp is a vital factor as the thermostat is calibrated to open and close as needed to keep the engine within it's optimal operating temp.
I say you can use the coolant/engine temp to know when that is, and others say you have to use the oil temp gauge. Cool, we have a difference of opinion. I'm just stating why I have my opinion.
However, notice that the oil temp gauge starts, and starts moving, at about 160-170F, or right about where the thermostat would open. That's not coincidental. I think it was done this way intentionally. Also notice that once the oil temp gauge starts to move, it moves fairly quickly, as if all this calibration is taking into account the coolant/engine temp.

It's like saying there was one successful combustion in a cylinder of your engine and it was at the right temp so now your car is operating at temperature. You are allowed what ever opinon you would like.

What? I don't get your point here. Also, what you just wrote is not MY opinion, it's your analogy, not mine.
So, using the coolant temp gauge to determine that proper engine temp has been reached, is like using one cylinders successful combustion, and that now indicates proper operating temp?
I don't know where that comes from, or really what it means.
But, if I try to understand it, you're implying that coolant/temp gauges are as inaccurate as taking the temp reading from one combustion chamber to then conclude the whole engine is at proper operating temp?
Well, that's NOT how the system works, so....

Ok, I think I've beaten this topic to death.
I welcome reading other peoples comments on this issue, and if you can post some sources that would be great to read too.
I'll try to restrain myself from anymore long posts, as I've said enough, too much for most people to bother reading.

In the Z4M the variable redline indicator on the tach doesn't reach the maximum until the oil temperature reaches 75C (167F), it's first major mark is at 50C, so BMW expects the oil to be at least at 75C before using the full rev range. For the Z4M the manual states that normal oil operating temperature is between 80C and 120C, with 100C being the centre position. All current oil specs quote the viscocity at 100C, so for example, a 0w40 oil is thicker than 40 weight below 100C and flows less easily, with a higher likelihood that the oil pump won't be able to pump a high enough volume of cold oil to keep the engine well lubricated at high revs.

I don't use the maximum rev range until the oil is at normal temperature, i.e. 80C, or beyond 120C (which I haven't reached on the track yet, it maxes out at about 115C under very hard use). It is interesting that BMW considers that oil temperature is more important in the ///M cars than water temperature.

With the 135i, I'll use a similar philosophy, when we receive the car in a couple of months.

For any engine, running it hard with cold oil will cause more stress on the components, it just depends on how much risk of wear you are willing to tolerate.

Yes, it's been a more common useage in the the M engines, but they also rev a lot higher.

Still, using the temps you quoted, it makes sense that the "go for it" oil temp is around the same temp as the thermostat would open.

In the M cars, have you noticed at what temp the coolant gauge is at when the oil temp gauge is showing 167F?

a 0w40 oil is thicker than 40 weight below 100C and flows less easily, with a higher likelihood that the oil pump won't be able to pump a high enough volume of cold oil to keep the engine well lubricated at high revs.

That's not right. "Viscosity" is the resistance to flow. So a 30 weight oil will be less viscous than a 40 weight when hot. Higher weight oil is, or should be, MORE viscous and thins less when temps get really hot.

A 0W40 is a "Winter" rated oil, meaning in sub freezing temps the oil retains it's ability to flow, or low viscosity. The "40" rating means that at higher temps it's just like a straight 40 weight oil, greater viscosity.
Amazing stuff this. Of course, go too hot and the oil starts to lose it's viscosity.
At cold temps, straight 40 weight would be too viscous to flow properly, and the pump would have a heck of a time getting straight 40 to flow in sub freezing temps, and the oil will be too thick to properly lubricate rings, bearings, etc...

Yes, it's been a more common useage in the the M engines, but they also rev a lot higher.

Still, using the temps you quoted, it makes sense that the "go for it" oil temp is around the same temp as the thermostat would open.

In the M cars, have you noticed at what temp the coolant gauge is at when the oil temp gauge is showing 167F?

a 0w40 oil is thicker than 40 weight below 100C and flows less easily, with a higher likelihood that the oil pump won't be able to pump a high enough volume of cold oil to keep the engine well lubricated at high revs.

That's not right. "Viscosity" is the resistance to flow. So a 30 weight oil will be less viscous than a 40 weight when hot. Higher weight oil is, or should be, MORE viscous and thins less when temps get really hot.

A 0W40 is a "Winter" rated oil, meaning in sub freezing temps the oil retains it's ability to flow, or low viscosity. The "40" rating means that at higher temps it's just like a straight 40 weight oil, greater viscosity.
Amazing stuff this. Of course, go too hot and the oil starts to lose it's viscosity.
At cold temps, straight 40 weight would be too viscous to flow properly, and the pump would have a heck of a time getting straight 40 to flow in sub freezing temps, and the oil will be too thick to properly lubricate rings, bearings, etc...

The current ///M cars do not have a water temperature gauge, just an oil temperature one. A warning light will illuminate if the engine is over temp.

I wasn't talking about a straight 40 weight oil in my comment, maybe I should have phrased it better - the 40 part of 0w40 (the 40 weight, not straight 40) is measured from a specification perspective at 100C. At any temperature less than 100C, the oil is going to be thicker than the engineers envisioned by specifying that weight of oil, it is going to act like a heavier weight oil (just because it is cold) and flow through the engine in a more viscous manner, meaning that the oil pump will have less flow than if the oil was at the specified temperature for the grade measurement (100C)

So oil temp at 200*F is officially considered "operating temperature"?

I think he said that it was "warm" at 200, not necessarily at normal operating temps.
My temp in normal driving is about 240 or so (it was 250 before I got the BMW PPK) and it takes me 10-15 for the gauge to oil temp gauge to climb up to that number.